In general, a black-and-white silver halide photographic light-sensitive material is exposed to light imagewise and is then photographically processed in a process comprising 4 steps, namely, a developing step, a fixing step, a washing step and a drying step. Most of the developing steps are carried out with a developing solution comprising hydroquinone and phenidone or metol in combination. It is usual to contain a sulfite in the developing solution for preventing any oxidation of a developing agent and improving the preservability of the developing solution, because the developing step is carried out in an alkaline condition. However, the sulfite has a nature of dissolving a silver salt. Therefore, a silver salt is dissolved out of a photographic light-sensitive material in the course of carrying out a developing step. The silver salt dissolved in the developing solution is reduced and deposited to become a metal silver. The deposited metal silver then adheres to the surface of the light-sensitive material, so that a silver stain may be produced. Particularly in a high-temperature and rapid process carried out through an automatic processor, such a silver stain as mentioned above becomes problematic.
When an amount of a developing solution replenished is relatively smaller to a quantity of light-sensitive materials processed, the above-mentioned problem becomes more serious, because a deposited concentration of the metal silver is relatively increased. For solving the problem, some research on a compound have been so tried to improve a preservability without dissolving such a silver salt as mentioned above. However, no answer thereto has still been discovered. On the other hand, some research have also been tried on how to prevent any deposition by trapping a silver salt being dissolved. For example, a silver sludge preventive has widely been searched to obtain so far. U.S. Pat. No. 3,173,789 reports on a 1-phenyl-5-mercaptotetrazole derivative; Japanese Patent Publication Open to Public Inspection (hereinafter abbreviated to JP OPI Publication) No. 52-36029/1977, a disulfide compound; and JP Examined Publication No. 62-4702/1987, a 2-mercaptobenzimidazole derivative; respectively. However, in any method in which the above-mentioned substances are used, there have raised such an additional problem that a developing speed is slowed down, that a fixing speed is also slowed down because a developing solution is brought into a fixing solution in the next step, and/or that the function of a silver sludge preventive is put out because it is reacted with a developing solution being preserved for a long time.